In molecular-electronics manufacturing, there is a long-standing need to integrate or “anchor” a molecular wire into electronic circuitry. Molecular wires are substances or compounds that can transmit a signal between two points in a circuit. The signal is usually electronic, but it can be mechanical, optical, or even magnetic. And when the signal is electronic, the wires are often described as organic molecules with conjugated electronic systems that can effectively transmit electrons one dimensionally.
A molecular wire has one or more chemical functionalities that can bond to a metallic surface- and this is what secures the wire to a surface. These chemical functionalities are commonly referred to as surface anchors. Anchors also act as the wire-electrode interface. So it's important that the anchor provide a stable interface that facilitates the transmission of a signal.
A molecular wire becomes a molecular device when it bonds, via a surface anchor, to at least one electrode of an electronic circuit. A diode is such a molecular device. Molecular devices are used to control current characteristics or quantum effects on current-voltage behavior.
Many conventional surface anchors have a single sulfur atom that chemically bonds with a subject metallic surface, i.e., surfaces of electronic circuitry. So when these types of sulfur-based anchors are employed, the target substrate is typically coated with a thin gold film because a relatively strong bond forms between sulfur and gold. And although single sulphur-metal bonds do form, prior-art anchors based on single thiols or thioethers are inadequate because of: (1) the chemical instability that results from only a single bond with a target substrate and (2) the resulting surface orientation is unpredictable. More specifically regarding surface orientation, anchors that form only a single sulfur-metal bond with a metallic surface have a surface orientation that is often uncontrollable and unpredictable. For example, such an anchor's surface orientation could be either substantially vertical or substantially parallel to a metallic-film surface. Unpredictable surface orientation is problematic because it directly impacts the spatial orientation of the entire molecular wire.
The art can therefore be improved by providing anchors with improved stability and more predictable surface orientation compared to prior-art single-sulfur anchors. More specifically, the art can be improved with anchors that form multiple sulfur-metal bonds.